1. Technical Field
This invention relates to fish tapes of the type used by electricians to pull wire through conduit or other spaces, and more particularly to the construction of a non-conductive fish tape assembly.
2. Description of the Related Art
A fish tape is an elongated “wire” or flexible rod typically used to install wire in conduit or through existing walls by pushing the tape through the conduit or wall, attaching the wire, and pulling it back. Steel fish tape is often used because it is stiff enough to be pushed through conduit without collapsing or kinking, flexible enough to negotiate bends or turns, and strong enough to pull multiple wires back through the conduit without breaking or separating under what can be considerable pulling forces. The steel tape can be flat in that has a smaller thickness than width, which aids in the ability to “steer” the tape as it is pushed through the wall or conduit. However, steel may be disadvantageous because it is heavy, possibly too rigid for tight bends, and importantly because it can conduct electricity, it may not be suitable for use near live circuits with open contacts, such as in switch boxes or fuse/breaker panels.
Fish tape made of plastic fibers, such as fiberglass, have been devised to avoid the aforementioned concerns with steel fish tape. Namely, such fish tapes are lighter, more flexible and do not conduct electricity, while at the same time providing high tensile strength. Because fiberglass can splinter, it may be covered by an extruded plastic jacket having better wear and toughness characteristics that is also of lower coefficient of friction to allow it to slide through the wall or conduit easier. The fiberglass or fiberglass composite fish tapes are typically extruded rods having a circular cross-section. The circular cross-section is disadvantageous in that makes the fish tape less steerable and adds to its thickness such that it requires more space when wound in the reel.
Long lengths of fish tape are used, for example 25 ft., 50 ft. and 100 ft. lengths are standard, because the fish tape is snaked through walls and conduit. To make the long run of fish tape manageable during use and storage it is use typically wound about a reel. One end of the fish tape is usually fixed to a stationary or rotatable part of the reel to keep it from coming loose. The other, leading end of the fish tape is adapted in some way to readily attach the wire to be pulled by the fish tape through the wall or conduit. For steel tapes, the ends may be turned back into a “U” or a loop to directly hook onto or loop about a catch inside the reel at the trailing end or the wires at the leading end. However, it is not possible to bend fiberglass fish tapes to form a hook or loop. Thus, tips must be attached to the ends of a fiberglass fish tape that have some type of attachment member. At the leading end, the attachment member is often an eyelet through which the wire can be tied.
The connection to the reel can be problematic. The tape may disengage the catch, or worse, the tape may break when high pulling loads arise. The latter problem can arise when the fiberglass tape is connected to reel in way that extends it radially relative to the reel. When the fish tape is completely unwound from the reel and pulling loads are applied, a bending moment is applied to the fish tape which can cause it to fracture.
The tip at the leading end of the fish tape can also be problematic, most commonly with regard to its ability to feed through the wall or conduit and its connection to the fish tape. The tip is usually a steel piece, however it may be plastic, see e.g. the ferrule item 17 disclosed in U.S. Pat. No. 3,858,848 to MacFetrich. The leading end of a tip for a steel tape usually has flat tapered sides, while for a fiberglass tape it is usually bullet-shaped with a spherical or conical due to the circular cross-section of the fiberglass rod. Considerable effort has been undertaken to lessen the resistance in the feed direction, however, this still remains a problem.
Various techniques have been used to attach the tip to the fish tape including depending on the materials and configuration of the tip used. Welding and threaded attachments are common for steel fish tapes. Fiberglass fish tapes typically employ a friction connection, such as crimping, or an adhesive. A taper-lock connection can be used in which the fish tape is inserted into a conical bore in an externally threaded inner part of the tip and then expanded in the bore by threading a screw into the end of the tape bore the outer part of the tip is threaded onto the inner part. Although various methods of connection have been devised, it is common for tips to pull off of the fish tape under high pulling loads or to loosen after prolonged use.
Accordingly, a non-conductive fish tape assembly is desired with improved construction of the fish tape and end pieces.